refactor: Centralize role types and configuration (#190)

Creates a single source of truth for all worker roles via lib/roles/.

## New: lib/roles/

- **registry.ts** — All role definitions (dev, qa, architect) with
  levels, models, emoji, completion results, session key patterns
- **types.ts** — RoleConfig interface
- **selectors.ts** — Query helpers: getRole(), getLevelsForRole(),
  resolveModel(), isValidResult(), roleForLevel(), etc.
- **index.ts** — Barrel exports

## Migrated Files

- **lib/tiers.ts** — Now delegates to registry (backward compat kept)
- **lib/dispatch.ts** — Uses registry for emoji resolution
- **lib/bootstrap-hook.ts** — Uses registry for session key pattern
- **lib/services/tick.ts** — Uses registry for level detection
- **lib/services/heartbeat.ts** — Uses registry for role iteration
- **lib/tools/health.ts** — Uses registry for role iteration
- **lib/tools/work-start.ts** — Uses registry for role enum
- **lib/tools/work-finish.ts** — Uses registry for result validation
- **lib/tools/project-register.ts** — Uses registry for level lists

## Key Benefits

- Adding a new role = add entry to registry.ts (single file)
- No more scattered role unions ("dev" | "qa" | "architect")
- Type-safe role/level/result validation from registry
- Session key pattern auto-generated from registry
- All 64 tests passing (22 new registry tests + 42 existing)

lib/roles/registry.ts

@@ -0,0 +1,75 @@
+/**
+ * roles/registry.ts — Single source of truth for all worker roles.
+ *
+ * Adding a new role? Just add an entry here. Everything else derives from this.
+ *
+ * Each role defines:
+ * - Identity (id, displayName)
+ * - Levels and models
+ * - Emoji for announcements
+ * - Valid completion results
+ * - Session key matching
+ * - Notification preferences
+ */
+import type { RoleConfig } from "./types.js";
+
+export const ROLE_REGISTRY: Record<string, RoleConfig> = {
+  dev: {
+    id: "dev",
+    displayName: "DEV",
+    levels: ["junior", "medior", "senior"],
+    defaultLevel: "medior",
+    models: {
+      junior: "anthropic/claude-haiku-4-5",
+      medior: "anthropic/claude-sonnet-4-5",
+      senior: "anthropic/claude-opus-4-5",
+    },
+    emoji: {
+      junior: "⚡",
+      medior: "🔧",
+      senior: "🧠",
+    },
+    fallbackEmoji: "🔧",
+    completionResults: ["done", "blocked"],
+    sessionKeyPattern: "dev",
+    notifications: { onStart: true, onComplete: true },
+  },
+
+  qa: {
+    id: "qa",
+    displayName: "QA",
+    levels: ["reviewer", "tester"],
+    defaultLevel: "reviewer",
+    models: {
+      reviewer: "anthropic/claude-sonnet-4-5",
+      tester: "anthropic/claude-haiku-4-5",
+    },
+    emoji: {
+      reviewer: "🔍",
+      tester: "👀",
+    },
+    fallbackEmoji: "🔍",
+    completionResults: ["pass", "fail", "refine", "blocked"],
+    sessionKeyPattern: "qa",
+    notifications: { onStart: true, onComplete: true },
+  },
+
+  architect: {
+    id: "architect",
+    displayName: "ARCHITECT",
+    levels: ["opus", "sonnet"],
+    defaultLevel: "sonnet",
+    models: {
+      opus: "anthropic/claude-opus-4-5",
+      sonnet: "anthropic/claude-sonnet-4-5",
+    },
+    emoji: {
+      opus: "🏗️",
+      sonnet: "📐",
+    },
+    fallbackEmoji: "🏗️",
+    completionResults: ["done", "blocked"],
+    sessionKeyPattern: "architect",
+    notifications: { onStart: true, onComplete: true },
+  },
+};